Coking of hydrocarbon oils



Nov. 7, 1939. J. G. ALTI-IER COKING 0F HYDROCARBON OILS original FiledMarch 51, 193e INVENTOR JOSEPH G. ALTHER f BY vATTORNEY Patented Nov.v'1,1939

PATENT OFFICE 2,179,080 oolnNG or mRocARBoN ons Joseph G. Alther,Chicago, Ill., assignor to Universal Oil Products Company, Chicago,lll., a corporation ofl Delaware Continuation of application Serial No.71,898, March 31, 1936. `This application February 20,

1939, serial No. 257,288

2 Claims.

This is a continuation of my application, Serial No. 71,898 filed March3l, 1936, which has now become abandoned.

This invention particularly refers'to an im- Y proved process andapparatus for the pyrolytic conversion of heavy' hydrocarbon oils, suchas residual oils, particularly those resulting from the cracking of olower boiling oils and also including mixtures of hydrocarbon oil andsolid or semi-solid pyro bituminous materials, such as coal, accompaniedby continuous coking of the resulting tar-like residue on a continuousconveyor by means of heat applied directly to the upper surface of arelatively thin bed .o f said heavy pitch-like residue on the conveyor.

, Many operations have previously been proposed for the continuouslvcoking ofV heavy residual' oils. Some of these employ externally heatedrotary retorts or continuous conveyors of vaporous types wherein theheat for coking is passed through metal or refractorymaterial upon whichthe coke is deposited. Obviously, this necessitates excessive heating ofthe metal or refractory surface upon which the coke is deposited invorder tc supply suicient heat through the bed of material undergoingcoking to effectively coke its upper portions and, even when thematerial to be coked is confined to a relatively thin layer the usefullife of 'the heated surface upon which the coke is deposited` isrelatively short and the characteristics of the coke produced varyconsiderable, particularly with respect to volatilityand hardness, dueto excessive heating of the lower portions of the layer and insufcientheating of the upper portions. Other operations which have been proposedapply heat directly to the upper surface 'of the materials undergoingcoking by combustion in the vapor space above the coke bed which,v ofcourse, involves at least partial combustion of the volatilehydrocarbons-evolved from the materials undergoing coking Each of thesetwo types of operations possess certainadvantages. By employing the rstmentioned process contaminationof the volatiles evolved from thematerials undergoing coking with combustion gases and/ or actualcombustion of the hydrocarbons evolved may be prevented while, byemploying the second mentioned process, excessive heating of the surfaceupon which the coke accumulates may be avoided. The present inventionretains the advantages of both of the previously proposed processesabove mentioned and obviates the disadvantages of each.

Another method of continuous coking which is now used extensivelyprovides for introducing the relatively heavy oil to be coked in highlyheated state into alternately operated coking zones wherein coking isaccomplished either by the excess heat contained in the heavy oilsupplied to i furnace structure.

the coking zone or by introducing a suitable heat carrying medium intothe body of material undergoing coking. This is probably the mostsatisfactory method which has been employed for coking heavy residualoils such as those resulting from cracking but involves the rathercumbersome and inefficient procedure of switching and preconditioningthe coking zones. The present invention also retains the advantages ofthis method, which eliminates the disadvantages of both of the othermethods previously described, and in addition obviates the use ofalternately operated coking zones.

In the preferred embodiment of the invention, the relatively heavy oilto be coked is passed through the heating coil of a furnace, which ispreferably of the general type previously disclosed by me, wherein it is.quickly heated,under non-coking conditions, to a sufficiently hightemperature to eiect subsequent substantial coking thereof. The highlyvheated oil is then passed into a separating zone preferably operated atsubstantially atmospheric or relatively low superatmospheric pressurewherein its vaporous components are separated from the resultingnonvaporous liquid residue, the vaporous products are removed from theseparating zone and may 'be subjected to condensation for the recoveryof their condensable components and separation of the same fromuncondensed gases or they may rst be subjected to fractionation for theseparate recovery of one or more selected intermediate or high-boilingfractions, The liquid residue, which is separately removed from theseparating zone at high temperature in the form of a relatively heavypitch-like residue, is continuously discharged onto the upper surface ofa continuous belt-type conveyor disposed within a suitable caused tospread out in a relatively thin body of extended surface over the uppersurface of the moving conveyor-belt and is reduced thereon to arelatively thin mass of coke-like material partially by its containedheat and partially by heat radiated thereto by the relatively hotrefractory walls of the combustion chamber of the coking The coke-likemass then continues pn the coking furnace which maybe relatively smallin relation to the whole furnace structure and is The pitch-like residueis.

separated from the remaining portion thereof by refractory walls,preferably of` high heat conductivity, which radiate heat to thematerials undergoing, coking in the preceding zone of the cokingfurnace. Combustible materials are introduced directly into thecombustion chamber and heatis supplied from the resulting hot combustiongases and the hot refractory walls of this zone directly to the uppersurface of said relatively thin coke-like mass upon the conveyor wherebyits reduction to relatively dry coke is completed after a substantialamount of volatiles have been evolved therefrom in the preceding zone ofthe coking furnace, out of contact with the combustion gases. Combustionproducts are removed from the combustion zone without allowing anysubstantialquantity thereof to commingle with the volatiles evolved inthe preceding coking stage, the latter being returned to the separatingzone wherefrom they are removed to subsequent treatment with the othervaporous products from this zone and the coke is subsequently removedfrom the conveyor and discharged from the system, quenching. Y

The advantages which accrue from the various features of the inventionwill be apparent. to those familiar with ordinary cracking and cokingoperations from the above description and from the accompanyingdiagrammatic drawing and following description thereof. The drawing is aview in side elevation, with parts in section, of one specific form ofapparatus in which the operation of the process maybe accomplished. y

Referring to the drawing, the heavy oil charging stock, which maycomprise, for example, liquid residue from a cracking operation o'r fromstorage or any other heavy fluid or semi-fluid hydrocarbon from anyJiesired source, is supplied through line I and valve 2 to pump 3 bymeans of which it is fed through line 4 and valve 5 to the heating coilof the system which is located within furnace 6.

Any desired type of furnace may be employed which is capable of quicklyheating the heavy oil to a suiiiciently high temperature to effect itssubsequent reduction to heavy pitch or` cokelike residue, Withoutallowing it toremain in the heating coil for'a'suicient length of timeto permit substantial coke formation and deposition therein. 'Ihefurnace here illustrated is of the general type previously disclosed byme which is now generally known in the industry as an equiflux heater.This term is derived from the fact that the main portion of the heatingcoil or fluid conduit indicated in the drawing atl is comprised of aplurality of tubes which are each subjected to substantially equal ratesof heating on opposite sides. case here illustrated, comprises twovertical rows of horizontally disposed tubes 8 arranged in staggeredformation so that the opposite sides of each tube are exposed to radiantheat transmitted thereto from the hot refractory side walls 9 and I0 ofthe furnace and the materials undergoing combustion in combustion zonesII and I2 located, respectively, between tube bank 'I and walls 9 andI0. Regulated amounts of fuel and air are supplied to each of thecombustion zones by means of burners I3 communicating with each of thecombustion zones through firing ports I4 in the roof of the furnace,through which firing ports controlled amounts of auxiliary air and/orrecirculated combustion gases may be introduced. In the particular casehere illustrated, adjacent tubes in opposite rows of bank 1 areconnected at their ends in series by means of suitable return bends, asindicated in the drawing by the single lines connecting adjacent tubesin opposite rows, and preferably substantially equal heating conditionsare maintained in combustion zones Il and` I2 although, when desired,

adjacent tubes in each row of bank 1 may be connected in series anddierent ring conditions may be maintained in combustion zones II andpreferably after Tube bank '1, in the I2. Preferably the burners I3 arepointed at an angle toward the side walls 9 and I0 so that the flames.and hot combustion gases impinge upon and Wash the refractorywalls,.heating the same to a highly radiant condition. Since one of thepurposes of a furnace of this type is to provide exceptionally highrates of. heat transfer to the'ol passing through tube bank 'I byemploying predominantly radiant heat from the walls and hot combustiongases on opposite sides of each tube, the combustion gases leave zonesII and I2 at a relatively high temperature and, preferably, in order toincrease the furnace eiliciency by recovering additional heat .from thegases, a separate tank of tubes, in'dicated in the drawing at I5, isprovided beneath combustion zones'II and I2 and between these zonesvandflue I6. In this manner heat is imparted to the tubes of bank I5 both byradiation and convection from the combustion gases passing from zones Iland I2 to flue I6. Flue I6 communicates with a suitable stack, notillustrated, and a suitable damper, not illustrated, may be providedeither in the stack or the ue. In the case here illustrated, the heavyoil to be treated flows in a general upward direction through tube bankI5 countercurrent to the general direction of flow of the combustiongases and thence passes through tube bank 1, in the manner alreadydescribed, to be discharged at a relatively high conversion temperaturefrom the uppermost tube of this bank through line I1 and valve I8 intothe separating zone I9. n

The heavy residual tar-like products separate from the vaporouscomponents of' the prodso I rected rapidly downward through the lowerportion of the separating zone to the coking zone 20 wherein they passonto the moving surface of conveyor 2I to be reduced thereon to arelatively thin bed of coke. The vaporous products which separate -fromthe relatively heavy pitch-like residue in zone I9 are removed from theupper portion thereof through line 22 and valve 23 and may be eithersubjected to condensation and the resulting distillate and gas collectedand separated or they may be first subjected to fractionation for theseparate recovery of any desired intermediate or high-boiling fractions.This portion of the apparatus may be of any well known form and'for thesake of simplicity is not illustrated in the drawing.

Conveyor 2|, which is motivated by any suitable means, not illustrated,may be any desired type or form of conveyor capable of retaining thepitch-like residue from zone I9 upon its upper surface in a relativelythin body. The conveyor, in the case here illustrated, is a continuousbelt-type employing a belt of suitable metal or metallic alloy capableof withstanding pitch-like residue on the conveyor before it is coked.Preferably in order to minimizev coke deposition in zone I9 there is nosubstantial restrictionin the path of flow of the heavy pitchlikeresidue from this zone to the surface of the conveyor and in the casehere illustrated a.

the conditions to which it issubjected and having upturned or flangededges 24 to retain the' belt 2| in order to prevent the heavy pitch-likeresidue from flowing over the end of the conveyor. Any other suitablespreading or distributing device may, of course, be employed within thescope of the invention.

Conveyor 2 l is disposed within a suitable insulated housing or furnacesetting 26 and a portion of the coking zone, which is indicated in thedrawing as combustion chamber 21 is separated from the remaining portionby means of suitable walls 28, preferably constructed of refractorymaterial of high heat conductivity such as, for example, siliconcarbide. Walls 28 extend horizontally between the side walls of thefurnace setting 26 and extend vertically from the roof of the furnace orfrom a point above the main portion of the roof to near the surface ofthe coke-like material on the conveyor. In this manner combustion zone21 is effectively separated from the .rest of the coking zone and gasesresulting from the combustion fuel in this zone are thereby preventedfrom commingling with and contaminating the hydrocarbon vapors evolvedfrom the materials undergoing coking in other portions of the cokingzone. Suitable burners, the tips of which are indicated in the drawingat 29, communicate with combustion zone 21 through firing ports 30whereby combustible fuel and air is supplied to thiszone and, whendesired, the burners may be pointed at an angle toward the refractorywalls 28 in order that the hot combustion gases may impinge upon andwash the walls, heating the same to a high temperature.

Heat is radiated from the materials undergoing combustion in chamber 21and from the interior surface of the refractory walls of this zone tothe bed of cokelike material on conveyor-belt2l as it passes immediatelybeneath the combustion zone. Combustion gases are removed from the upperportion of combustion zone 21 through ue 3l controlled by damper 32 to a'suitable stack, not

illustrated, and preferably'pass on their way to the stack through aneconomizer section, not illustrated, which may serve, for example, as ameans of preheating air for either or both combustion zone 21 andfurnace 6. Preferably the draft through flue 3l is so controlled thatthere is a slight flow of hydrocarbon vapors and gases into combustionzone 21 from the other portions of the coking zone rather than a flow ofcombustion gases from zone 21 into the other portions of the cokingzone.

Preferably combustion chamber 21 is located a substantial distance alongthe path of travel of the materials undergoing coking on conveyor 2|from the inlet end of the conveyor so that when the material on theconveyor reaches zone 21 it will have been substantially reduced to cokeand a major portion of the volatiles will have been evolved therefrom inthe preceding portion of the coking zone. In this manner the heatsupplied to the coke-like material on conveyor 2| passing beneathcombustion chamber 21 will serve to reduce the volatility of the coke tothe desired degree after a major portion of the vaporizable hydrocarbonshave been liberated from the heavy pitch-like residue from zone I9. Aspreviously mentioned, walls 28 preferably comprise amaterial of highheat conductivity so that heat will4 be transmitted through these wallsto the materials on the conveyor in other portions of the coking zone toassist vaporization of a major portion of the volatiles from thepitch-like residue before it n reaches the combustion. chamber.

Hydrocarbon vapors and gases evolved from gases previously separatedfrom the pitch-like residue -in this zone or they may be separatelysupplied to suitable condensing or fractionating equipment, not shown.When desired, suitable means, such as baffles, bubble trays, or thelike, may be provided in the upper portion of separating zone I9 toassist in removing any entrained or dissolved heavy pitch-like or otherhigh coke-forming materials from the hydrocarbon vapors and gases, priorto their removal from this zone.

The layer of coke on the conveyor, after passing beneath combustionchamber 21, passes to the discharge end of the conveyor'from which it isremoved through a suitable discharge port 35, which may be sealed eitherby mechanical means, not illustrated, or by maintaining a suitableliquid level in the discharge port, such as indicated at 36. In theparticular case here illustrated, a suitable conveyor 31 is providedbeneath discharge port 35 to remove the coke to cars, not illustrated,or to storage or elsewhere, as desired, and preferably the lower'end ofIconveyor 31 is immersed in the same liquid which ser'ves to sealdischarge port 35, the coke being thereby quenched before it is removedto the atmosphere.

When desired, a suitable spray arrangement, indicated at 38, maybe'provided to introduce water or other suitable cooling material ontothe bed of coke at the discharge end of the conveyorv to causecontraction of the coke and facilitate its removal from the conveyor. Asuitable scraper 39 is also preferably provided to complete removal ofthe coke from the conveyor belt.

In an apparatus such as illustrated, and above described, the preferredrange of operating conditions which may be employed to produce thedesired results are approximately as follows:

ample, from a superatmospheric pressure of 30 pounds or less per squareinch to 150 pounds or more per square inch. In order to assist quickseparation of vapors and gases from the pitchlike residue following theheating step the sep arating zone is preferably operated atsubstantially atmospheric or relatively low superatmospherlc pressureand substantially the same pressure is preferably employed in the cokingzone.

The bed of coke-like material is preferably heated,

vas itpasses beneath the combustion chamber of the coking zone, to atemperature of from 1000 to 1500 F., or more, in order to insure theproduction of a low volatile, relatively dense coke of uniform qualityand good structural strength.

As a specic example of the operation of the process as it may beaccomplished in an apparatus such as illustrated and above described,

the charging stock for the coking operation is a gases, discharging saidpitch-like residue from heavy residue of about 4b A. P. I. gravityderived from the cracking of a Mid-Continent topped.

-ber connected in series and followed by a reduced pressure vaporizingand separating chamber, 'fractionating condensing and collectingequipment with reflux condensate from the fractionator returned to thecracking coil. When operated without the coking step the crackingconditions in such a system may be controlled to produce approximately60 per cent of good quality motor fuel and about 30 per cent of heavyresidue of about 4 A. P. I. gravity. In the present case thetemperature.- and pressure conditions employed in the cracking systemare maintained substantially the same and the heavy cracked residue fromthe reduced pressure and separating chamber of the cracking system ispassed through the heating stage of the coking system wherein it isquickly heated to a temperature of approximately 975 F. at asuperatmospheric pressure of about 50 pounds per square inch, withoutallowing it to remain in the heating coil and succeeding separating zonefor a suilicient length of time to permit any substantial formation anddeposition of coke in these zones. The heavy pitch-likexresidue from theseparating zone is discharged onto the conveyor and after being reducedto a coke-like mass by its contained heat and heat transmitted theretofrom the refractory walls of the combustion chamber in the coking zoneit is passed beneath the combustion chamber and heated at this `point toa temperature of approximately l300 F. 'I'he bed of coke at thedischarge end of the conveyor ls cooled by spraying with water, theresulting contraction causing it to loosen from the conveyorbelt andit-is removed therefrom in relatively large pieces, further quenched anddischarged to storage. Vaporous products and gases from the separatingzone and from the coking zone are gas. 'The coke produced is ofexceptionally low volatility, uniform quality and goodstructuralstrength.

I claim as my invention:

l. A process for the cracking and coking of heavy hydrocarbon oils,which comprises quickly heating the oil tol a high conversiontemperature while passing the same in a continuous stream through aheating coil subjected to high rates of heating by heat radiateddirectly to its surface from materials undergoing combustion and the hotrefractory confining Walls, introducing the heated products into aseparating zone wherein the resultant heavy pitch-like residue separatesfrom their Vaporous components, removing said Vaporous components fromthe separating zone, subjectingthe same to condensation and separatingtle resulting condensate'and uncondensed the separating zone onto themoving surface of a continuous conveyor within a coking zone causing thepitch-like residue to spread out -in a relatively thin layer over theupper surface of the conveyor and reducing it thereon to a relativelythin mass of coke-like material by means of its contained heat and bymeans of heat radiated thereto from the relatively hot refractory wallswhich separate the coking zone from the combustion chamber, passing thecoke-like material on the conveyor beneath said combustion chamber atwhich point coking and devolatilization of the coke to the desireddegree is completed by heating the material on theconveyor toa hightemperature by heat radiated directly to its upper surface frommaterials undergoing combustion in said combustion chamber and the hotrefractory walls thereof, removing resulting combustion gases from saidcombustion chamber without permittingv any. appreciable quantity thereofto commingle with the hydrocarbon vapors and gases evolved wi thin andseparately removed from said coking zone outside said combustionchamber, and continuously removing the 'deposited bed of coke from `theVconveyor and quenching and discharging the same from the system.

2. A process for the cracking and coking of heavy hydrocarbon oils,which comprises quickly heating the oil to a high conversion temperaturewhile passing the same in a continuous stream through a heating coilsubjected to high rates of heatingby heat radiated directly to itssurface from materials undergoing combustion and the hot refractoryconfining walls, introducing the heated products into a Separating zonewherein the resultant heavy pitch-like residue separates from theirVaporous components, removing said Vaporous components from theseparating zone, subjecting the same to condensation and separating theresulting condensate and uncondensed gases, discharging said pitch-likeresidue from the separating zone onto the moving surface of a continuousconveyor` within a -coking zone causing the pitch-like residue to spreadout in a relatively thin layer over the upper surface of the conveyorand reducing it thereon to a relatively thin mass of coke-like materialby means of its contained heat and by means of heat radiated theretofrom the relatively hot refractory walls which separate the coking zonefrom the combustion chamber, passing the coke-like mai terial on theconveyor beneath said combustion chamber at which point coking anddevolatilization of the coke to the desired degree is completed byheating the material on the conveyor to a high temperature by heatradiated directly to its upper surface from materials undergoingcombustion in said combustion chamber and the hot refractory wallsthereof, removing resulting combustion gases from said combustionchamber Without permitting any appreciable quantity thereof to comminglewith the hydrocarbon vapors and gases evolved within and separatelyremoved from said coking zone outside said combustionchamber,`commingling the last mentioned vapors and gases with thosepreviously separated from the heated products in said separating zone,and continuously removing the deposited bed of coke from the conveyorand quenching and discharging the same from the system.

JOSEPH G. ALTHER.

